Dr. Daniel PotterMegan Simpson always expected that she would be a mother to a daughter.

She had grown up in a family of four sisters. She liked sewing, baking, and doing hair and makeup. She hoped one day to share these interests with a little girl whom she could dress in pink.

Simpson, a labor and delivery nurse at a hospital north of Toronto, was surprised when her first child, born in 2002, was a boy. That’s okay, she thought. The next one will be a girl.

Except it wasn’t. Two years later, she gave birth to another boy.

Desperate for a baby girl, Simpson and her husband drove four hours to a fertility clinic in Michigan. Gender selection is illegal in Canada, which is why the couple turned to the United States. They paid $800 for a procedure that sorts sperm based on the assumption that sperm carrying a Y chromosome swim faster in a protein solution than sperm with an X chromosome do.